SCEV update problem


   We come across a ScalarEvolution (SE) problem the other day. It seems to
be a fundamental design problem. I don't think I have a clean and cheap fix to
this problem. I talked with Andy in the phone yesterday, he told me it is a
known fundamental problem. But I don't see any discussion on this problem on the
list, so I post the problem here, soliciting your insightful comment.

  Tons thanks in advance!


   I don't know for sure if I can post the reduced *.ll (2k+ lines) to
the list. Let me try my best to describe this problem without *.ll.

   Let me start from 5k feet high.